Stainless Steel Alloy 803
UNS S35045 · also Incoloy alloy 803
Iron-nickel-chromium heat-resistant superaustenitic alloy with titanium/aluminum additions for precipitation strengthening, giving high strength and resistance to carburization and oxidation at elevated temperature.
Reference datasheet — Alloy 803 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
Alloy 803 tempers and conditions
Alloy 803 is supplied in 5 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed (mill annealed plate, sheet, bar, tube) | Default stocked condition: maximum ductility and creep performance for furnace tubes, coils and fabricated hardware. | 265 | 585 | 45 | 165 HB | — |
Cold drawn and re-annealed tube/bar | Best combination of tight dimensions, fine grain and full high-temperature ductility for pyrolysis and reformer tubing. | 270 | 590 | 45 | 160 HB | 1.7 % IACS |
Hot finished | Pick for heavy bar, thick plate and extruded tube where mill hot-finishing plus anneal is the economical route. | 285 | 600 | 40 | 175 HB | 1.7 % IACS |
Stress relieved | Use when residual stresses from forming or welding must be lowered while retaining part of the cold-work strength. | 380 | 660 | 32 | 14 HRC | 1.7 % IACS |
Cold drawn | Choose for close-tolerance bar/tube needing higher room-temperature strength; not for long-term high-temperature creep service without re-annealing. | 460 | 720 | 25 | 20 HRC | 1.7 % IACS |
What is Alloy 803?
Iron-nickel-chromium heat-resistant superaustenitic alloy with titanium/aluminum additions for precipitation strengthening, giving high strength and resistance to carburization and oxidation at elevated temperature. Alloy 803 has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 59% of stainless steel grades. It melts at 1,345°C (2,453 °F). Alloy 803 has a yield strength of 265 MPa (38.4 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 81% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
What is Alloy 803 used for?
- petrochemical furnace components
- ethylene cracking equipment
- radiant tubes
- high-temperature fixtures
Advantages
- High service temperature — 1,100°C (2,012 °F), better than 96% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Poor heat conductor — 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 96% of stainless steel grades
- Low electrical conductivity — 1.7 % IACS, worse than 93% of stainless steel grades
- Low strength — 265 MPa (38.4 ksi), worse than 81% of stainless steel grades
Alloy 803 properties
Typical room-temperature values for Alloy 803-Annealed; bars are the position among stainless steel grades.
Physical3
Alloy 803 has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 59% of stainless steel grades. It melts at 1,345°C (2,453 °F).
Mechanical13
Alloy 803 has a yield strength of 265 MPa (38.4 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 81% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
Alloy 803 is rated for continuous service to 1,100°C (2,012 °F). It conducts heat at 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades. Thermal expansion is 14.8 µm/m·K (8.22 µin/in·°F).
Electrical3
Alloy 803 conducts electricity at 1.7 % IACS, worse than 93% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 73% of stainless steel grades.
Sustainability4
Producing a kilogram of Alloy 803 takes about 100 MJ of energy and emits 7 kg of CO₂ — more than 98% of stainless steel grades. Typical recycled content is 40%.
Manufacturability8
Alloy 803's machinability is poor (27/100, worse than 83% of stainless steel grades); weldability good (65/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. Alloy 803 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Alloy 803
Is Alloy 803 easy to machine?
Machine like alloy 800H but tougher: rigid setups, positive-rake carbide, low speed / heavy positive feed, flood coolant and no dwelling to avoid work-hardened glaze.
Can Alloy 803 be welded?
Readily GTAW/GMAW/SMAW welded with matching 803 or Ni-Cr-Nb (ERNiCr-3 / 617-type) filler; keep heat input low, no preheat needed, avoid long dwell in the 650–900 °C sigma/carbide range.
Can Alloy 803 be formed, bent or molded?
Good hot workability at 1050–1200 °C; cold forms well but work-hardens fast — allow extra power, generous bend radii and intermediate anneals at 1100–1150 °C followed by rapid cooling.
Alloy 803 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ni | 32 – 37 | 34 |
| Cr | 25 – 29 | 27 |
| Ccarbon kept high for creep strength | 0.06 – 0.1 | 0.08 |
| Al | 0.15 – 0.6 | 0.3 |
| TiAl+Ti 0.30–1.20 total | 0.15 – 0.6 | 0.4 |
| Si | ≤ 1.5 | 0.7 |
| Mn | ≤ 1.5 | 0.8 |
| Cu | ≤ 0.75 | 0.1 |
| S | ≤ 0.02 | 0 |
| Febalance, 34.5 % min per ASTM | balance |
What surface finishes work on Alloy 803?
Descale by pickling or grit blasting after hot work; passivate for cleanliness. Not anodizable; paint/plating rarely used since the Cr₂O₃ scale is the working surface.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel Alloy 803 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S35045
- Trade names
- Incoloy alloy 803
How much does Alloy 803 cost?
Alloy 803 is a high-cost stainless steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Alloy 803 — frequently asked
What is Alloy 803 used for?
Alloy 803 is typically used for petrochemical furnace components, ethylene cracking equipment, radiant tubes and high-temperature fixtures. In short: carburization-resistant furnace alloy; service to 1100 °C; ti/Al precipitation strengthened.
What is the yield strength of Alloy 803?
Alloy 803 has a typical yield strength of 265 MPa (38.4 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 81% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is Alloy 803 easy to machine?
Not especially — machinability is rated poor (27/100, worse than 83% of stainless steel grades). Machine like alloy 800H but tougher: rigid setups, positive-rake carbide, low speed / heavy positive feed, flood coolant and no dwelling to avoid work-hardened glaze.
Can Alloy 803 be welded?
Yes — weldability is rated good (65/100). Readily GTAW/GMAW/SMAW welded with matching 803 or Ni-Cr-Nb (ERNiCr-3 / 617-type) filler; keep heat input low, no preheat needed, avoid long dwell in the 650–900 °C sigma/carbide range.
What surface finishes work on Alloy 803?
Descale by pickling or grit blasting after hot work; passivate for cleanliness. Not anodizable; paint/plating rarely used since the Cr₂O₃ scale is the working surface.
Can Alloy 803 be formed, bent or molded?
Good hot workability at 1050–1200 °C; cold forms well but work-hardens fast — allow extra power, generous bend radii and intermediate anneals at 1100–1150 °C followed by rapid cooling.
What is the maximum service temperature of Alloy 803?
Alloy 803 is rated for continuous use to about 1,100°C (2,012 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alloy 803 Annealed and Alloy 803-CD?
Annealed is the default condition — default stocked condition: maximum ductility and creep performance for furnace tubes, coils and fabricated hardware. CD: choose for close-tolerance bar/tube needing higher room-temperature strength; not for long-term high-temperature creep service without re-annealing. Yield strength is 265 MPa in Annealed versus 460 MPa in CD.
How much does Alloy 803 cost?
Alloy 803 is a high-cost stainless steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- INCOLOY alloy 803 technical bulletin — Special Metals Corporation (2004)
- ASTM B409 — Ni-Fe-Cr Alloy Plate, Sheet and Strip — ASTM International (2021)
- ASTM B407 — Ni-Fe-Cr Alloy Seamless Pipe and Tube — ASTM International (2019)
- ASTM B408 — Ni-Fe-Cr Alloy Rod and Bar — ASTM International (2019)
- ASM Specialty Handbook: Heat-Resistant Materials — ASM International (1997)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.